1 Field of the Invention
The invention relates to a centrifugal pump for delivering a fluid as well as to a centrifugal pump system. The invention relates in particular to a centrifugal pump and a centrifugal pump system for delivering blood.
2 Description of the Prior Art
WO-A-96/31934 teaches a rotary pump and especially a centrifugal pump in which the impeller is mounted to float inside the pump housing by magnetic forces, and driven by a rotating field generated by a stator located outside the pump housing. According to the principle of the so-called bearingless motor, the stator is designed as a bearing and drive stator and the rotor is integrated into the impeller and designed as a bearing and drive rotor. Pumps of this kind are especially advantageous for those applications in which the fluid to be delivered must not be contaminated, for example for delivering biological fluids such as blood or highly purified fluids such as super-pure water. Rotary pumps of this kind are also suitable for delivering aggressive fluids, which would destroy mechanical bearings in a short time. Centrifugal pumps of this kind are used, for example, as blood pumps to maintain circulation during open heart surgery. It is also possible to use such pumps as artificial hearts. In this case, it is necessary to use at least two separate pumps. One pump takes over the function of the left ventricle and keeps the systemic circulation functioning while the other pump takes over the function of the right ventricle and maintains the pulmonary circulation. The use of at least two separate pumps to perform the heart function, however, involves a relatively large space requirement that proves to be a limitation especially when it comes to implantation of such pumps as artificial hearts.